On Wed, 12 Jan 2005 01:39:03 +0000, Mark Rand
wrote:

On Tue, 11 Jan 2005 21:40:03 GMT, Mr G H Ireland wrote:

I thought that welding transformers were built with a large leakage
inductance, so that the arc is struck with a higher voltage, which falls to
10-15volts as soon as the arc strikes.
I believe a power transformer would not behave like that - a transformer
with good regulation would burn out in seconds if it were used for welding,
unless there were some current-limiting in circuit.

Perhaps somebody who knows could enlighten me?

G.H.Ireland

They are built like that. A separate variable inductor could be used for
current control in series with a normal power transformer to give the same
'nominally constant current' effect.

Yes, but a ferro-resonant transformer as shown does current-limit.
If the cross-leg were sawn and made adjustable, it might behave a lot
like an arc welder.